Electrical control system



y 5, 1953 EACHUS, JR 2,637,831

ELECTRICAL CONTROL SYSTEM Filed Sept. 9, 1949 3 Sheets-Sheet l -IG 33 w ae T ,3 .64

: s v a/llHkC, SUPPLY a V e AC. SUPPLY 40 42 o. c. SUPPLY /ZG Filed Sept. 9, 1949 May 5, 1953 l. EACHUS, JR

ELECTRICAL CONTROL SYSTEM 3 Sheets-Sheet 2 5 NC FIG. i

U '5' '6' 8 TIME SuPbLY VOLTAGE APPLIED ELECTRODES uovlue TOGETHER GAS DISCHARGE was COMDUCQIMG UOHCOUDUCTIUG 1 on o "/0 J I '5' ..s FIG. 3 E) 2 r. O TIME ARC STRUCK zmo VOLTAGE ELECTRODES TOUCH-HUG GAS DIsCHARGE TUBE cououc-rms UOUCOMDyCTIUG 0% loOo J 3 Fl G. 3C

0 TIME mac-moves MOVUJG APART GAS DISHARGE was COUDUCTIHG UONCOHU JCTIHG 0% \oc'u c I NC J 5' I 3 FIG. 5D I Q Q TIME o ELECTRODES MOVING FURTHER APART. 1310672201". GA ovscums: TUBE Becki! fiacfiusrfir COUUU TING HOD-JCOUDU TING 0v? mo /5 1W I5 Sheets-Sheet 3 TUBE a uoucououcnus A MORE THAN 50% 6A5 mscHAEzcE TUBE NONCOUDUC'HHG LESS THAN so SLOWLY APART GAS D15 CHARGE COLJDUC'HNG Twla ELECTRODES MOVING MORE HME eunums .RAIsEs o.c. LEVEL LESS THAN 50 ELECTRODES MGVE TOGETHER Fn G. 3 F

cowouc-rme MORE THAN so 1 6 E m; a?

l. EACHUS, Jl

ELECTRICAL CONTROL SYSTEM F! a. 3 E

TUBE

H G. 3 G

FI 3H 1 l l -so -*so%-- STATIONARY HOUCOUDUCTHJG TIME ELECTRoDEs GAS D\5CHARGE COHDUC'HN G May 5, 1953 Filed Sept. 9, 1949 'HME. CORE MATERIALS FALLlUCi \NTO ARC Lgwa: D.EI/.ELE EA\T ELECTR 0e MO GAS mscr-mnqa TUBE fig; Z2;-

uoucououcT-mc; g 49 MORE THAN 50% COUDUCHUG Less THAu 50 Patented May 5, 1953 UN IT ED- STATES PAT E-NT OFFIQE ELEGTRIGAL: EONTROL SYSTEM Macbeth ArcLain'p (30., Philadelphia, Pa a;

corporation ofiennsylvania" Application September 9, 1949, SerialNo. 114,819

7 Claims. (01. err-e l) This invention relates to electrical control systems of the type embodying, voltage-responsive control or an adjustable device. Inits more 1ir'nitedlaspect,.the invention relates to controloi arc lamps.

The principal object of theinvention is to provid'eahig-hly eiiicient servo system of the voltagere'sponsive type.

A more specific object of the invention is to provide an improvedsystem for thecontrol of arc lamps. e

While it is intended. that the servo system provided by the present invention shall be utilized for control'purpos'es wherever it may find useful application, the invention isespecially adapted? to arclamp control and thereforeit will be described with specific reference thereto.

Th'epresent invention evolved from-an extensive study and investigation'of arc lamp operation and control, an'd'from' extensive development work toward improved operation of. arc. lamps. in the past, are lamps have not been entirely satisfactory; and careful investigation has shown that:

this" has been due to the fact that the available control systems have been inadequate to provide the type of control action that is necessary to maintain stea'dy light intensity. I'he two factors? which de'term'in'e the' light intensity of an-arclamp' arefthevoltage across the arc andthe current flow." Th'e' voltag'e across the arc is proportional to the length of the arc gap which, becomes.-

greater as theelectrodes burn away. It is there-- fore ,,necessary to adjust the length of the arc gap to" maintain a substantially constant voltage there'a'cross, if the light intensity of the arc is-to 1 he maintained substantially constant; However,

prior systems for automatically adjusting the lengthof th'e'arc gap have not been entirely satisfactory;

By the-present invention there is provided a rapid -action servo system of the v'oltage-respon-- sive' type which iscapable'ofcontroiling an arc lamp in a highly efiicient manner. As an additional feature, WhBIE'A. C. operation of anarc lamp'is'" desired, the invention" provides forv rel atively slow action control of the arc current. This latter control is achieved by the use of aconstant current transformer: The dual control, provided using boththe servo system and" the'constant current transformer, is highly desirable, although the servo system maybe" used alone where it is desired to supply D. C. to an arc lamp.

'I 'he ihventionmay be fully understood by ref erence to'the'accompanying drawings in which: Fig. 1 is a diagrammatic illustration of system may be considered to be carbon electrodes of. an

arc-lamp.v These electrodes are connected across, the secondary 3 of a constant current transformer 4 whose primary 5'is connected to a suitable fi C. source by means of supply conductors 6. The

' source of A. C. voltage may be a 2 20 volt, GO cycle source. The constant current transformer 4 servesas-the relatively slow-acting ballast control means hereinbeiore mentioned, and it serves to regulate the current supplied tothe arc lamp electrodes independently of therapid-actingvoltage responsive. control arrangement now to bede scribed.

The positioning of the electrodes I and 2 is effected by means of. a conventional two pha'se reversible motor designated generally. by reference character 1. The motor shaft may be, con-- nected to reducing gears 8, the dotted line 9 representing the mechanical connection. The posi tioning. oftheelectrodes maybe eiiected by means of gear racks m and. H connected respectivelyto the electrodes l and Landhaving associatedth'erewith a common pinion or driving gear I2 which is. driven from the reduction gears 8; through theme'chanical connection represented by the" dotted line [3. It will be seen that rota tion of. gear I2 in one direction will cause the electrodes l' and 2 to move toward one another,

while rotation of saidgearin the opposite direction will cause the electrodes to move away from each other. e 7

Th'ereversiblemotor 1" is-controlled by a relay ['4 having. an energizing winding l5 and: a movable contact it which is pivoted at H- and is: adapted to engage either o'f'the stationary con- A biasing spring 2!! urgesthe movable contact l5. toward contact [9,-- and when these contacts are engaged, the motor l iscaused to operate ina direction to effect. separation-of the electrodes land 2; Therelay winding [5 acts against the spring 20; andwhen the relay-is ener=- gized, themovable contact I5 is urged toward contact I 8. Engagement of these two contact-s causes the motor to operate in the: direction to" efi'ect movement of the electrodes l1 andZ-toWard one another.

The motor I may be energized from the same voltage source which supplies the electrodes. The motor may be a 110 volt motor and it may be supplied by means of conductors 2| and 22, conductor 21 being connected to a suitable tap on the primary winding E, and conductor 22 bein connected to one of the supply conductors 6. It will be seen that conductor 2| extends to the pivoted end of the movable relay contact it, while conductor 22 is connected to the junction of the field windings of motor '3. Contacts 58 and 89 are connected via conductors 23 and 2t to the other ends of the motor field windings.

The voltage across electrodes I and 2 is supplied via conductors 25 and 25 to the primary winding 2? of a transformer 28. The secondary winding 29 of this transformer is connected to a control circuit which includes a rectifier 30, filter components which may comprise resistors 3!, 32, 33, and condensers 3t, 35, 36, a gas-discharge tube ?i'l, and the relay winding I5. The filter components may be varied considerably and some of them may be omitted, depending upon the specific application.

The control circuit above described effects rapid action control of the positioning of electrodes I and 2 in response to the voltage across the electrodes. Thus, there is provided a rapid-action servo system which is responsive to variations of the voltage across the electrodes and which functions to maintain the voltage constant during operation of th arc lamp, independently of the current-controlling action of the constant current transformer t.

The operation of the servo system will now be described in detail with reference to Figs. 3A to 3H. In these figures, the line C represents the starting voltage level of tube 37, i. e., the level which must be reached by the applied voltage to render the tube conductive. Line NC represents the non-conducting voltage level of the tube, i. e., the voltage level below which the tube becomes non-conductive. V represents the applied voltage.

In the inoperative state of the system, i. e., with the supply source disconnected, the spring 2K3 is effective to maintain contact it in engagement with contact I9. When the system is placed in operation by the connection of the supply source, the motor l is operated in a direction to effect the movement of the electrodes 9 and 2 away from each other. At the same time an A. C. potential is applied to the control circuit through transformer 28. The voltage appearing on the secondary winding 29 is rectified by rectifier 30 and is filtered by the filter comprising components 3i to 36. The rectified voltage, which appears across the gas discharge tube 37, is as shown at V in the illustrations of Figs 3A to 31-1, having D. C. and ripple components dependent upon the relative sizes of the filter components. This voltage varies with changes in the arc voltage, as may be seen from the illustrations. When the supply source is first connected, the voltage across the gas discharge tube 31 will be in excess of the amount necessary to cause it to conduct, as may be seen in Fig. 3A. Current will flow through relay winding I5, and movable contact it will be drawn to the stationary contact It so that the rotation of the motor 7 will move the electrodes l and 2 toward each other. Electrodes I and 2 will continue to move together until an arc is struck. At this time the voltage across the electrodes I and 2 and the control transformer 28 will have dropped to zero. Consequently, the voltage across the gas discharge tube 37 will have dropped to zero so that it will be in a non-conducting state (see Fig. 3B). There will be no current through relay winding I5, and biasing spring 29 will return movable contact It to engage with stationary contact I9. Thus the voltage applied to motor '5 will cause it to rotate in a direction which will move electrodes I and 2 apart. A voltage will appear across the tube 31 but it will not be of sufiicient amplitude to start the tube (see Fig. 3C).

As the electrodes I and 2 move apart the voltage across the arc, which also appears across the control transformer 28, increases. In turn, the voltage induced in the secondary 29 and the voltage across the gas discharge tube 3! will increase (see Fig. 3D). The rate at which this voltage increases will depend upon the relative sizes of the components in the filter circuit. The electrodes I and 2 will continue to move apart at a rapid rate until the voltage across the gas discharge tube 3'! has increased to such a value that the peak of that voltage exceeds the level C necessary for conduction (see Fig. 3E). The gas discharge tube tl will start to conduct and will continue to conduct until the value of the voltage across the tube drops below the level NC required to maintain conduction. The length of time that the tube will conduct will increase as the electrodes l and 2 move farther apart, until the gas discharge tube 3'! is conducting 50% of the time (see Fig. 33). When this is the situation, the movable contact it will dwell equally upon both stationary contacts I8 and I9 so that the motor 'I will be motionless.

As the lamp burns the electrode material is consumed, lengthening the arc gap and causing the arc voltage to rise. The increase of the voltage across the control transformer 28 will increase the voltage across the gas discharge tube 31 so that it will conduct for more than half the time (see Fig. 3G). Contact It will dwell on contact It for more than half the time and the rotation of the motor I will bring the electrodes I and 2 toward each other until the proper arc gap is obtained.

Similarly when core material falls into the arc, the distance between the electrodes I and 2 is reduced and the voltage across the arc decreases. This decrease in the voltage across the primary 2? of control transformer 28 will result in a lowered voltage across the gas discharge tube 3'! so that it will conduct for less than half the time (see Fig. 3H). The movable contact I 6 will dwell on contact is for more than half the time so that the net rotation of the motor I will be to move the electrodes I and 2 apart until the proper distance between the electrodes I and 2 has been restored and the electrodes become stationary.

From the foregoing description, it will be seen that the motor l is controlled according to theconductivity or non-conductivity of the electron tube 37, and the relative time percentages of conductivity and non-conductivity of said tube are varied according to the amplitude of a controlling voltage.

An important advantage of the system is that in controlling both fields of the motor I, the restoring torque will vary approximately as the square of the deviation from the null position. This permits the use of a sensitive and smoothoperating feed mechanism without the use of additional mechanism or electrical damping elements. lhe apportionment of the three condensers and the three resistors in the filter cir- 5. cnit; amends; the sensitivity and" shape of the; torque; error: curve: to be; varied, i111 such a man-'- njern to v be most. advantageous; to; the: particue lax: application; involved,

In; 2;, there is illustrated a: modified form: of the-system: in: which: a D. C; voltage is appliedto;.the electrodes. In this; instance; V the: constant; current; transformeridaoi Fig.1 isqeleminat'ed, and: an; interrupter 38; is provided as shown so} as to supply aa-simulated A Ci voltage to. the, controltransformen 28;. The, interruptermay. berini the. form; of: as relay having a:..\vindin 38;. a movable contact 40; and-stationary contactsv M. and 4'2 Bothithel-motor I. andthe. relay Mia-may be: ener-- giaedzfrom acommonAzC. supply ovenconductors 43-2. Aside from the" aboveementioned: modifications the system is: identical: with tha lmf Land-elements aredesignated-by. the same referencanumerals; 'I heroprration of the'syst'em;of Fig; 1 2" is the, same as a the operation of the; sys1;-: temof Fig. jl-a's-described above;

Thefpresenttinvention has gone into coznmer cialzusei and hasiproved to be highly successful; In; one: physical embodiment according to Eig5. l, the: gas'discharge tube 3:1 is a miniature type 9132; relay; Mzis a-Western Electric' RelayiType 275B; rectifier 3011801" the seleniuintype; and tlie filterrcomponents have values-.astfollows:

Resistor 3 l i(non'e requiredft'his'. arrangement)? Resistor32 loo-seams Resistor 33 4000 ohms. Condenser 34 2 microfarads Condenser 35" Z'microfarads Condenser 36" microfarad;

The transformer 28 has a step downiratio,.of:l5'5 for an arc ,voltageoffZSvolts.

While certain embodiments of the invention haveibeen illustrated and-described, the'invention is not limited: thereto; but" is capable:- of other forms of physical expression.

7 Moreover, the servo system provided by. themventioniisi'not limited-to arc lamp controll' By way" off example of other" uses; this system. has been" applied to the maintenance of constant speed'in magnetic sound recording devices. Oblviously this system may be.utilizedwherever it'is desired. to maintain some condition anddt is convenient to provide an A. C. voltage which varies with that condition.

I claim:

1. In a servo system for control of an adjustable device; means including a reversible motor for adjusting said device; a single controlling relay having a winding, a pair of spaced stationary contacts, and a movable contact biased toward one of the stationary contacts and movable toward the other stationary contact upon energization of said winding; reversing connections for said motor connected to the relay contacts for control of said motor by said relay; a single gas-discharge tube in circuit with the winding of said relay to control the same, said tube becoming conductive at a certain voltage level and becoming non-conductive at a certain lower voltage level; and means for applying to said tube a cyclically fluctuating unidirectional voltage whose amplitude varies in relation to said voltage levels according to the adjustment of said device, whereby the relative time percentages of conductivity and nonconductivity of said tube are varied accordin to the adjustment of said device, and said motor is controlled accordingly through the operation of said relay under control of said tube.

2. In a servo system for control of an adjustsaidmotor: connected,- to= the relay.- contacts for control oft said-motorby saidirelayg; aicontrol 0111-- cuit'. forv supplying current, to, the" winding of said relay ;2.a .single gas-discharge tube. in: said; circuit to control saidsrelay; \sa-idi tube. becoming: conductive; at certain; voltagedevel:v and becoming nonconductive at: a certain lowervolt'a'ge levels and 1 means: for: producing: in: said; circuit across: said? tubeia cyclically"fluctuatingunidirectionalvoltage whose ia'mplitudetvaries in relation to I said voltage. levels' acco'rdingitoi theadjust'ment of said device;v whereby the relativetimel percentagesr ofconducttiv-ity and noni-conductivity of saidi tuberarer var-' ied according: to the adjustment of said device; and said-motor is: controlled; according-1y through the cper'ation of saith relay under: eonti olof said tube},

I n' a servo system foi control of an; adjust able device gj means: including a reversible motor for-adj ting saiddev asingl'e controlling re:

lay having awinding; :9; pain oi spaced' stationany soutacts, and-- a movable contact biased: toward I (meof the stationary contacts and ino /able toward the other stationary contact uponienergiaa ti-oirof said winding; eversing. connections for said motor connected to: the relay contacts for conti'ol of said motor by said relay; atcontrol ciri cuit -for supplying currentto the v idingof said K amplitudevaries in i relation to said volta'ge levels according; to the adjustmentof said device;

whereby the relativeti'me percentages of conduc tivity and non-conductivity ofsaid tube ar'e var led according to the adjustment of said device; and said motor is controlled accordingly through the operation of said relay under control of said tube.

4. In a servo system for control of an adjustable device; means including a reversible motor for adjustin said device; a single controlling relay having a winding, a pair of spaced stationary contacts, and a movable contact biased toward one of the stationary contacts and movable toward the other stationary contact upon energization of said winding; reversing connections for said motor connected to the relay contacts for control of said motor by said relay; a gas diode which becomes conductive at a certain voltage level and becomes non-conductive at a certain lower voltage level; a control circuit including said diode and the winding of said relay in series; a transformer connected to supply current to said control circuit; means for supplying to said transformer an alternating voltage whose amplitude varies according to the adjustment of said device; and rectifying and filtering means in said control circuit for converting the voltage from said transformer to a cyclically fluctuating unidirectional voltage whose amplitude varies in relation to said voltage levels according to the adjustment of said device, whereby the relative time percentages of conductivity and non-conductivity of said diode are varied according to the adjustment of said device, and said motor is controlled accordingly through the operation of said relay under control of said diode.

5. In a servo system for control of an arc lamp; means including a reversible motor for adjusting the lamp electrodes; a single controlling relay having a winding, a pair of spaced stationary contacts, and a movable contact biased toward one of the stationary contacts and movable toward the other stationary contact upon energization of said winding; reversing connections ,for said motor connected to the relay contacts for control of said motor by said relay; a single gas-discharge tube in circuit with the winding of said relay to control the same, said tube becoming conductive at a certain voltage level and becoming non-conductive at a certain lower voltage level; and means responsive to the voltage across said electrodes for applying to said tube a cyclically fluctuating unidirectional voltage whose amplitude varies in relation to said voltage levels according to the voltage across said electrodes, whereby the relative time percentages of conductivity and non-conductivity of said tube are varied according to the voltage across said electrodes, and said motor is controlled accordingly through the operation of said relay under control of said tube.

6. In a servo system for control of an arc lamp; a constant current transformer for supplying operating current to the arc lamp; means including a reversible motor for adjusting the lamp electrodes; a single controlling relay having a winding, a pair of spaced stationary contacts, and a movable contact biased toward one of the stationary contacts and movable toward the other stationary contact upon energization of said winding; reversing connections for said motor connected to the relay contacts for control of said motor by said relay; a single gas-discharge tube in circuit with the winding of said relay to control the same, said tube becoming conductive at a certain voltage level and becoming nonconductive at a certain lower voltage level; and means responsive to the voltage across said electrodes for applying to said tube a cyclically fluctuating unidirectional voltage whose amplitude varies in relation to said voltage levels according to the voltage across said electrodes, whereby the relative time percentages of conductivity and non-conductivity of said tube are varied according to the voltage across said electrodes, and said motor is controlled accordingly through the operation of said relay under control of said tube.

7. In a servo system for control of an arc lamp; means for supplying unidirectional current to the arc lamp; means including a reversible motor for adjusting the lamp electrodes; a single controlling relay having a winding, a pair of spaced stationary contacts, and a movable contact biased toward one of the stationary contacts and movable toward the other stationary contact upon energization of said winding; reversing connections for said motor connected to the relay contacts for control of said motor by said relay; a single gas-discharge tube in circuit with the winding of said relay to control the same, said tube becoming conductive at a certain voltage level and becoming non-conductive at a certain lower voltage level; means for deriving a simulated alternating voltage from the voltage across the lamp electrodes; and means responsive to the derived voltage for applying to said tube a cyclically fluctuating unidirectional voltage Whose amplitude varie in relation to said voltage levels according to the voltage across said electrodes, whereby the relative time percentages of conductivity and non-conductivity of said tube are varied according to the voltage across said electrodes, and said motor is controlled accordingly through the operation of said relay under control of said tube.

IREDELL EACHUS, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,885,155 Suits Nov. 1, 1932 2,259,958 Levy Oct. 21, 1941 2,293,079 Ranke Aug. 18, 1942 2,454,107 Wald Nov. 16, 1948 2,460,638 Gilbert Feb. 1, 1949 2,518,222 Carpenter et a1 Aug. 8, 1950 2,534,958 Deming Dec. 19, 1950 

